Borussia Dortmund took a glimpse into next season when Mario Goetze left the field early at the Santiago Bernabeu on Wednesday.

The playmaker, who walked off gingerly in the 13th minute clutching his hamstring, subjected his side to a further 77 minutes without him, and in turn showed them what it's like to play a crucial game absent his presence.

BVB scraped through after losing 2-0, but in fairness had four or five chances to put the tie to bed.

Dortmund had started in a customary 4-2-3-1 formation, with Goetze as a No. 10 sandwiched between Marco Reus (left) and JakubBlaszczykowski (right).

After the injury, Reus moved centrally and Kevin Grosskreutz—a former key player in JurgenKlopp's side and a great friend of Goetze's—came in on the left.

Reus doesn't start centrally often. According to WhoScored?, he's started just five games as a No. 10 this season and played almost solely on the flanks for BorussiaMoenchengladbach the season before.

At the Bernabeu, Reus slotted in pretty seamlessly. He drifted between the lines—which became increasingly stretched as the game went on—nicely, worked every area of the pitch and still managed to get in behind the defence.

In the second half, the speedster hit the byline and fizzed a perfect ball across the box to IlkayGundogan, who only needed to keep his calm for an easy, game-winning finish. The midfielder failed.

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But Dortmund, and in particular the regular advanced midfield trio, have set high standards: Would Klopp want to move Reus into the No. 10 role on a permanent basis next season and lose his dynamic, counterattacking abilities out wide? Is Grosskreutz a strong enough presence to be a regular starter on the left?

These are questions that will be answered by Dortmund's summer purchases and how the club lineup during preseason games.

At the very least, Klopp knows he has the players right now to look more than serviceable should no Goetze replacement materialise, and BVB aren't about to go and spend big bucks to place a guy on high wages.

But there are going to be options this summer, and one that could go a long way to plugging the gap is Christian Eriksen of Ajax; the Dane's contract expires in the summer of 2014, and he is widely expected to leave.

And what of Moritz Leitner or Leonardo Bittencourt? Both youngsters need game time, and perhaps Klopp will accept his summer losses as a setback, but also a chance to blood the very next Goetze.

Reus impressed centrally and naturally drifts around when operating from the left anyway, but the smart money is on Klopp replacing Goetze with a youth product or a new player.

Reus has proven himself capable in the No. 10 role on a massive occasion, and that will allow Klopp a little safety net should he put faith in youth and it doesn't bear fruit immediately.